1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
artcher [175]
3 years ago
8

Need help what the awnser is.b - 6 = 21​

Mathematics
1 answer:
Alex787 [66]3 years ago
3 0
27 hope this helps!!!
You might be interested in
Carly sold 18 rolls of rapping paper. thats 2 times as many rolls as jasmine sold. how many rolls did they sell althogether
Nastasia [14]
Carly sold 18, Jasmine sold half that. Half of 18 is 9. 9 + 18 = 27.

Together they sold 27 rolls of wrapping paper. 
8 0
3 years ago
Please I need help in a rush
baherus [9]

Answer:

i think the answer is 392= 49/Q

3 0
3 years ago
Find the maximum volume of a rectangular box that is inscribed in a sphere of radius r.
zvonat [6]

Answer:

The maximum volume of a box inscribed in a sphere of radius r is a cube with volume \frac{8r^3}{3\sqrt{3}}.

Step-by-step explanation:

This is an optimization problem; that means that given the constraints on the problem, the answer must be found without assuming any shape of the box. That feat is made through the power of derivatives, in which all possible shapes are analyzed in its equation and the biggest -or smallest, given the case- answer is obtained. Now, 'common sense' tells us that the shape that can contain more volume is a symmetrical one, that is, a cube. In this case common sense is correct, and the assumption can save lots of calculations, however, mathematics has also shown us that sometimes 'common sense' fails us and the answer can be quite unintuitive. Therefore, it is best not to assume any shape, and that's how it will be solved here.

The first step of solving a mathematics problem (after understanding the problem, of course) is to write down the known information and variables, and make a picture if possible.

The equation of a sphere of radius r is x^2 + y^2 + z^2=r^2. Where x, y and z are the distances from the center of the sphere to any of its points in the border. Notice that this is the three-dimensional version of Pythagoras' theorem, and it means that a sphere is the collection of coordinates in which the equation holds for a given radius, and that you can treat this spherical problem in cartesian coordinates.

A box that touches its corners with the sphere with arbitrary side lenghts is drawn, and the distances from the center of the sphere -which is also the center of the box- to each cartesian axis are named x, y and z; then, the complete sides of the box are measured  2x,  2y and 2z. The volume V of any rectangular box is given by the product of its sides, that is, V=2x\cdot 2y\cdot 2z=8xyz.

Those are the two equations that bound the problem. The idea is to optimize V in terms of r, therefore the radius of the sphere must be introduced into the equation of the volumen of the box so that both variables are correlated. From the equation of the sphere one of the variables is isolated: z^2=r^2-x^2 - y^2\quad \Rightarrow z= \sqrt{r^2-x^2 - y^2}, so it can be replaced into the other: V=8xy\sqrt{r^2-x^2 - y^2}.

But there are still two coordinate variables that are not fixed and cannot be replaced or assumed. This is the point in which optimization kicks in through derivatives. In this case, we have a cube in which every cartesian coordinate is independent from each other, so a partial derivative is applied to each coordinate independently, and then the answer from both coordiantes is merged into a single equation and it will hopefully solve the problem.

The x coordinate is treated first: \frac{\partial V}{\partial x} =\frac{\partial 8xy\sqrt{r^2-x^2 - y^2}}{\partial x}, in a partial derivative the other variable(s) is(are) treated as constant(s), therefore the product rule is applied: \frac{\partial V}{\partial x} = 8y\sqrt{r^2-x^2 - y^2}  + 8xy \frac{(r^2-x^2 - y^2)^{-1/2}}{2} (-2x) (careful with the chain rule) and now the expression is reorganized so that a common denominator is found \frac{\partial V)}{\partial x} = \frac{8y(r^2-x^2 - y^2)}{\sqrt{r^2-x^2 - y^2}}  - \frac{8x^2y }{\sqrt{r^2-x^2 - y^2}} = \frac{8y(r^2-2x^2 - y^2)}{\sqrt{r^2-x^2 - y^2}}.

Since it cannot be simplified any further it is left like that and it is proceed to optimize the other variable, the coordinate y. The process is symmetrical due to the equivalence of both terms in the volume equation. Thus, \frac{\partial V}{\partial y} = \frac{8x(r^2-x^2 - 2y^2)}{\sqrt{r^2-x^2 - y^2}}.

The final step is to set both partial derivatives equal to zero, and that represents the value for x and y which sets the volume V to its maximum possible value.

\frac{\partial V}{\partial x} = \frac{8y(r^2-2x^2 - y^2)}{\sqrt{r^2-x^2 - y^2}} =0 \quad\Rightarrow r^2-2x^2 - y^2=0 so that the non-trivial answer is selected, then r^2=2x^2+ y^2. Similarly, from the other variable it is obtained that r^2=x^2+2 y^2. The last equation is multiplied by two and then it is substracted from the first, r^2=3 y^2\therefore y=\frac{r}{\sqrt{3}}. Similarly, x=\frac{r}{\sqrt{3}}.

Steps must be retraced to the volume equation V=8xy\sqrt{r^2-x^2 - y^2}=8\frac{r}{\sqrt{3}}\frac{r}{\sqrt{3}}\sqrt{r^2-\left(\frac{r}{\sqrt{3}}\right)^2 - \left(\frac{r}{\sqrt{3}}\right)^2}=8\frac{r^2}{3}\sqrt{r^2-\frac{r^2}{3} - \frac{r^2}{3}} =8\frac{r^2}{3}\sqrt{\frac{r^2}{3}}=8\frac{r^3}{3\sqrt{3}}.

6 0
3 years ago
♡♡♡please help ♡♡♡<br>thank you ​
ElenaW [278]

Answer:

acute angle

Step-by-step explanation:

<h2><em><u>Finding the angle </u></em></h2>

an obtuse angle is an angle which is more than 90° but less than 180°

a right angle is 90°

a straight angle is 180°

an acute angle is less than 90°

is you look at the picture and the definitions you can notice that the angle is less than 90 ° hence its an <u>acute angle </u>

7 0
3 years ago
Read 2 more answers
In 2000, the population of Big Springs was 13 thousand. Use the given doubling
trasher [3.6K]

Answer:

The answer is "26179.4".

Step-by-step explanation:

Assume year 2000 as t, that is  t =0.

Formula:

A= A_0e^{rt}

Where,

A_0 = \ initial \ pop \\\\r= \ rate \ in \ decimal \\\\t= \ time \ in \ year

for doubling time,

r = \frac{log (2)}{t} \\

r = \frac{\log (2)}{ 40} \\\\r= \frac{0.301}{40}\\\\r= 0.007

Given value:

A = A_0e^{rt} \\\\

A_0 = 13000

t= 40 \ years

when year is 2000, t=0 so, year is 2100 year as t = 100.

A = 13000 \times e^{et}\\\\A = 13000 \times e^{e \times t}\\\\A = 13000 \times e^{0.007 \times 100}\\\\A = 13000 \times e^{0.7}\\\\A= 13000\times 2.0138\\\\A = 26179.4

7 0
3 years ago
Other questions:
  • I need help <br><br> Circle P is below
    7·2 answers
  • 1. 4/5 - (-3/10)=
    11·2 answers
  • Mya is selling tickets for the school
    11·1 answer
  • sue has 55 inches of ribbon. She wants to cut the ribbon into 6 equal pieces. How long will each piece be?
    8·1 answer
  • (+5)+(+6)+(+8)=2) (+6)+(+9)+(-3)
    10·1 answer
  • A teacher surveyed all 120 of her students about their lunch and lunch schedule. The teacher asked two questions:
    10·1 answer
  • Do the following pairs of equations represent parallel lines,
    15·1 answer
  • In ΔMNO, m∠M = 57° and m∠N = 75°. Which list has the sides of ΔMNO in order from shortest to longest?
    12·1 answer
  • Q.Find the selling price if the cost price is $1200 and loss percent is 25?
    11·1 answer
  • Rewrite using a single positive exponent 5^6/5^4
    15·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!